Burner control system



July-27, 1965 E. P. sELlNDER BURNER CONTROL SYSTEM Filed June 1'?, 1965 /II FLAME DETECTOR INVENTOR.

United States Patent O "ce 3,196,923 BURNER CONTRL SYSTEM Eric P. Seiinder, Palos Verdes Estates, Calif., assigner to Honeywell Inc., a corporation of Delaware Filed June 17, 1963, Ser. No. 238,275 4 Claims. (Cl. 158-28) This invention is concerned with an improved burner control system and particularly with such a system having a minimum number of components and being constructed and arranged to provide direct ignition of a main burner by the use of line voltage components.

The burner control system of my invention utilizes a unique bridge circuit construction by which an ignition means, in the form of an ignition transformer, and a fuel controller, in the form of a fuel valve, are connected in legs of the bridge circuit, the remaining legs of the bridge circuit being formed of resistors. The energization of the bridge circuit, by way of its input and output terminals, is controlled by a controller switch which is adapted to close upon the need for operation of an associated fuel burner unit, and by a normally closed switch of a safety cutout means having a bimetal and a heater which form a time delayed switch actuator.

A further portion of the bridge circuit includes a normally closed ame switch which is connected in parallel with the resistor bridge leg in series with the ignition transformer bridge leg. Thus, detection of flame is effective to place this resistor in series Vwith the ignition transformer to operatively de-energize the same upon the presence of flame.

The output terminals of the bridge are connected to the heater of the safety cutout means so that unbalance of the bridge is effective to operatively energize this heater. After a time period of heater energization, indicative of a failure to establish or maintain flame, cutout occurs and circuit means are provided to maintain the safety cutout means in this cutout condition by maintaining its heater energized. f

My invention will be apparent to those skilled in the art upon reference to the following specification, claims and drawing, ofwhich:

The `single figure is a schematic representation of a preferred embodiment of my invention.

Referring to the single figure, reference numeral designates a controller in the form of a thermostat bimetal switch which is responsive to the temperature of an area to be heated by an associated fuel burner, not shown. Upon the temperature of this area dropping, indicating a need for operation of the fuel burner, controller 10 closes its switch.

Closing of controller 1t) is effective, as willbe apparent, to energize a fuel valve 11 and an ignition transformer 12. Fuel valve 11 is connected in a fuel conduit, not shown, and is a normally closed fuel valve which is effective when operatively energized to allow fuel to flow to the fuel burner Where it is then ignited by means of ignition electrodes 13 connected to the secondary winding of ignition transformer 12.

A iiamdetector is shown in schematic form as having a closed switch 14 which is adapted to open on the presence of flame at the burner. An operator 15 is adapted to open switch 14 of the llame detector and this operator may be controlled electrically, as by a relay responsive to a photocell viewing the flame, or may be operated by a bimetal actuator, or similar actuator responsive to the presence of flame at the burner. It suffices to say that switch 14 opens on the presence of flame.

Reference numeral 16 identities safety cutout means having a bimetal 17, a heater 18 associated with bimetal 17 to form an actuator, a closed switch 19 and an open switch 2t). Energization of heater 1S for a given time 3,195,923 Patented July 27, 1965 period is effective to cause bimetal 17 to move in the direction of the arrow labelledH to open switch 19 and close switch 20.

As l have mentioned, my unique burner control system utilizes an arrangement in the form of a bridge circuit. This bridge circuit can be seen to have a first leg including a resistor 21, a second leg including the primary winding 22 of ignition transformer 12, a third leg including a .resistor 23, and a fourth leg including fuel valve 11. The

terminals identified by reference numerals 24 and 25 can be considered to be input terminals of the bridge circuit, whereas the terminals identified by reference numerals 26 and 27 can be considered to be the output terminals of this bridge circuit.

As can be seen, resistor 21 is shorted by flame detector switch 14 when this switch is in a position indicating the absence of flame. Also, the output terminals that is terminals 26 and 27 of the bridge circuit, are connected to opposite terminals of heater 18 of safety cutout means 16.

The input terminals 24 and 25 of the bridge circuit are connected to a pair of power line conductors 30 and 31 by means of a series circuit which includes the switch of controller ltl'and the closed switch 19 of safety cutou means 16.

Considering the operation of my improved burner control system, a call for operation of an associated fuel burner unit is evidenced by closing of controller 10. A circuit can now be traced from conductor 31 through controller 10, conductor 32, bimetal 17 and switch 19 of safety cutout means 16, input terminals 25 and 24 of the bridge circuit, and conductor 33 to the other power line conductor 30.

Fuel valve 11 is energized to pull in by way of a circuit which can be traced from bridge input terminal 25 through fuel valve 11, bridge output terminal 27, conductors 34 and 35, safety cutout means heater 1S, conductor 36, bridge output terminal 26, conductor 37, closed flame detector switch 14, and conductor 38 to power line Vconductor 30.

The primary winding 22 of ignition transformer 12 is operatively energized, to produce sparking at electrodes 13, by way of a circuit which can be traced from bridge input terminal 25 through primary winding 22, bridge output terminal 26, conductor 37, llame detector switch 14, Vand conductor 38 to power line conductor 30.

It should also be noted that circuits can be traced from bridge input terminal 25 to power line conductor 3d by way of fuel Valve 11 and resistor 23, and by way of primary winding 22 and resistor 21. However, the impedance magnitude of the resistors 23 and 21, respectively, are such that while limited electrical energization is applied to both the fuel valve and the ignition transformer through these circuits, the fuel Valve and the ignition transformer are not operatively energized by way of these circuits. Operative energization of transformer 12, and pull in of valve 11 requires that flame detector switch 14 be closed to establish the first above traced circuits.

More particularly, the impedance Value of resistor 23, connected in circuit with fuel Valve 11, is such as to maintain the fuel valve operatively energized, or pulled in, once it is initially pulled in by means of the first above traced circuit. The impedance value of resistor 21 is such that opening of flame detector switch 14 operatively de-energizes ignition transformer 12 to interrupt the sparking at electrodes 13 thereof.

Referring again to the initial energizing circuit of fuel valve 11, this initial energizing circuit includes inseries therewith heater 18 of safety cutout means 16 to opera- E means 16. Flame detector switch 14 then opens. The opening of this switch places resistor 21 in series with primary winding 22 of ignition transformer 12, and as above mentioned, operatively de-energizes this ignition transformer. Also, the opening of fiame detector switch 14 now causes fuel valve 11 to be maintained operatively energized through a circuit which can be traced from the bridge input terminal 25 through the fuel valve, bridge output terminal 27, resistor 23, bridge input terminal 24, and conductor 33 to power line conductor 39. As has been mentioned, this circuit supplies sufiicient electrical energy to the fuel valve to maintain the fuel valve energized, but not of a magnitude to initially operatively energize the fuel valve.

Heater 18 of safety cutout means 16 is connected across the output terminals 26 and 27 of the bridge circuit formed of the components 21, 22, 23 and 11. Once ame is detected, the bridge circuit is substantially balanced and heater 18 is operatively de-energized. This is the running condition of my improved burner control system.

If a flame failure is consequently experienced, flame detector switch 14 closes and the above described initial conditions are re-established whereby ignition transformmer 12 is again energized and the bridge is unbalanced to the extent that safety cutout means heater 18 is now energized.

If fiame is not subsequently re-established, safety cutout means 16 is effective, after a time period of energization of heater 18, to open switch 19 and close switch 20.

The opening of switch 19. disconnects the bridge input terminal 25 from the source of voltage 30-31.

The closing of switch 20 completes a series circuit which now connects the bridge output terminals 26 and 27 to power line conductors 3f) and 31. Since heater 18 is connected directly to these output terminals 26 and 27, heater 18 is likewise connected to the power line conductors 30 and 31. This can be seen by tracing a circuit from power line conductor 31 through controller 1t), conductor 32, bimetal 17 and switch 20 of safety cutout means 16, a resistor 4t), conductor 34, bridge output terminal 27, bridge output terminal 26, conductor 37, fiame detector switch 14, and conductor 38 to power line conductor 30.' Since heater 18 is directly connected to the bridge output terminals 26 and 27, heater 18 is maintained energized by way of this above traced circuit, resistor 40 functioning as a current limiting resistor. Thus safety cutout means 16 is maintained in an actuated or cutout condition, with switch 19 open and switch 26 closed. To reset safety cutout means 16 to the starting condition, it is necessary that controller be manually opened for a time period sufficient to allow bimctal 17 to cool and again close switch 19 and open switch 2t). The apparatus is then in a condtion to again attempt to establish tiame at the fuel burner. Thus, it is possible to reset safety cutout means 16 from a remote position, since electrical reset is provided.

From the above description, it can be seen that I have provided a unique burner control system wherein an ignition transformer and a fuel valve are connected in legs of a bridge circuit including limiting resistors, and wherein the bridge output terminals are connected to energize safety cutout means with switches of the safety cutout means and a flame detector switch being interconnected in the bridge circuit to provide safe and reliable operation of an associated fuel burner unit.

Modifications of my invention will be apparent to those skilled in the art and it is thus intended my invention be limited solely by the scope of the appended claims.

I claim as my invention:

1. Burner control apparatus in the form of a bridge circuit having first, second, third and fourth legs, and having input and output means, comprising; a pair of input terminals; a first resistor and ignition means connected in series between said input terminals to form the first and second legs of Ythe bridge circuit with the interconnection point being a first output terminal, a closed flame switch connected in parallel with said first resistor and movable to an open position in the presence of flame; a second resistor and a fuel valve connected in series bctween said input terminals to form the third and fourth 'regs of the bridge circuit with the interconnection point being a second output terminal; time delayed safety cutout means having a closed switch and a time delayed actuator adapted to open said switch after a time period of energization of said actuator; circuit means connecting said safety cutout means actuator between said first and second output terminals; and circuit means including said safety cutout means switch connecting said pair of input terminals to a source of voltage.

2. Burner control apparatus in the form of a bridge circuit having first, second, third and fourth legs, and having input and output means, comprising; a pair of input terminals; a first resistor and the primary winding of an ignition transformer connected in series between said input terminals to form the first and second legs of the bridge circuit with the interconnection point being a first output terminal, a closed flame switch connected in parallel with said first resistor and movable to an open position in the presence of tiame; a second resistor and a fuel valve connected in series between said input terminals to form the third and fourth legs of the bridge circuit with the interconnection point being a second output terminal; time delayed safety cutout means having a closed switch, an open switch, and a time delayed actuator adapted to actuate said switches after a time period of energization of said actuator; circuit means connecting said safety cutout means actuator between said first and second output terminals; circuit means including in series a switch controller and said safety cutout means closed switch connecting said pair of input terminals to a source of voltage; a third resistor, and circuit means including in series said switch controller, said third resistor, said flame switch, and said safety cutout means open switch connecting said first and second output terminals to a source of voltage upon failure to establish tiame during said time period.

3. Burner control apparatus for use with a fuel burner installation having an electrically energizable normally closed valve to control the tiow of fuel to a burner, and having electrically energizable ignition means associated with the burner to directly ignite the fuel, the apparatus being characterized as a bridge circuit having input terminals a and b and output terminals c and d, the apparatus comprising: a flame detector having a normally closed switch adapted to open upon the establishment of fiarne at the burner, a safety switch having an electrically energizable time delay actuator and a normally closed switch controlled thereby, circuit means connecting a first resistor between bridge terminals a and d to form a first leg of the bridge circuit, circuit means adapted to connect the valve between bridge terminals d and b to form a second leg of the bridge circuit, ciruit means adapted to connect the ignition means between bridge terminals b and c to form a third leg of the bridge circuit, circuit means connecting a second resistor and the normally closed switch of said flame detector in parallel between bridge terminals c and a to form a fourth leg of the bridge circuit, circuit means connecting said safety switch actuator between bridge terminals c and d, and circuit means including the normally closed switch of said safety switch adapted to connect bridge terminals a and b to a source of electrical voltage.

4. Burner control apparatus for use with a fuel burner installation having an electrically energizable normally closed valve to control the flow of fuel to a burner, and having electrically energizable ignition means associated with the burner to directly ignite the fuel, the apparatus being characterized as a bridge circuit having input terminals a and b and output terminals c and d,

5 the apparatus comprising: a ame detector having a normally closed switch adapted to open upon the establishment of flame at the burner, a safety switch having an electrically energizable time delay actuator and aV normally closed and a normally open switch controlled thereby, circuit means connecting a rst resistor between bridge terminals a and d to form a first leg of the bridge circuit, circuit means adapted to connect the valve between bridge terminals d and b to form a second leg of the bridge circuit, circuit means adapted to connect the ignition means between bridge terminals b and c to form a third leg of the bridge circuit, circuit means connecting a second resistor and the normally closed switch of said ame detector in parallel between bridge terminals c and a to form a fourth leg of the bridge circuit, circuit 6 means connecting said safety switch actuator between bridge terminals c and d, circuit means including the normally closed switch of said safety switch adapted to connect bridge terminals a and b to a source of electrical voltage, and circuit means including a third resistor and the normally open switch of said safety switch in series adapted to connect bridge terminals a and d to the source of electrical voltage.

References Cited bythe Examiner UNITED STATES PATENTS 2,380,125 7/ 45 Strobel 158-28 X 2,761,625 9/56 Dymski 158-28 X JAMES W. WESTHAVER, Primary Examiner. 

1. BURNER CONTROL APPARATUS IN THE FORM OF A BRIDGE CIRCUIT HAVING FIRST, SECOND, THIRD AND FOURTH LEGS, AND HAVING INPUT AND OUTPUT MEANS, COMPRISING; A PAIR OF INPUT TERMINALS; A FIRST RESISTOR AND IGNITION MEANS CONNECTED IN SERIES BETWEEN SAID INPUT TERMINALS TO FORM THE FIRST AND SECOND LEGS OF THE BRIDGE CIRCUIT WITH THE INTERCONNECTION POINT BEING A FIRST OUTPUT TERMINAL, A CLOSED FLAME SWITCH CONNECTED IN PARALLEL WITH SAID FIRST RESISTOR AND MOVABLE TO AN OPEN POSITION IN THE PRESENCE OF FLAME; A SECOND RESISTOR AND A FUEL VALVE CONNECTED IN SERIES BETWEEN SAID INPUT TERMINALS TO FORM THE THIRD AND FOURTH LEGS OF TEH BRIDGE CIRCUIT WITH THE INTERCONNECTION POINT BEING A SECOND OUTPUT TERMINAL; TIME DELAYED SAFETY CUTOUT MEANS HAVING A CLOSED SWITCH AND A TIME DELAYED ACTUATOR ADAPTED TO OPEN SAID SWITCH AFTER A TIME PERIOD 